1. Technical Field
The present invention relates to a semiconductor memory, and more particularly, to an apparatus and method for controlling a refresh operation of a semiconductor integrated circuit.
2. Related Art
In a semiconductor memory integrated circuit, particularly, a semiconductor memory integrated circuit used for mobile devices, a reduction in power consumption is an important indicators of performance. Therefore, a method of generating a refresh signal for a refresh operation, which is a necessary operation of the semiconductor memory integrated circuit, such that the period of the refresh signal is two to twenty times larger at a low temperature than that at a high temperature, is used.
Two types of period generating circuits are used to realize the above-mentioned method. One period generating circuit (first period generating circuit) generates a pulse having an uniform (that is, fixed) period without being affected by temperature. The other period generating circuit (second period generating circuit) generates a pulse whose period varies according to a variation in temperature.
The pulse generated by the second period generating circuit is used as a refresh signal at a temperature equal to or higher than room temperature, and the pulse generated by the first period generating circuit is used as the refresh signal at a temperature lower than room temperature.
However, even when only the pulse generated by one of the two period generating circuits is used as the refresh signal, the other period generating circuit is continuously operated, which causes unnecessary current consumption. In particular, when the second period generating circuit generates a high-frequency pulse (a pulse having a small period) under a high temperature condition, current consumption increases.